The ethics board said that Plouffe, who helped Uber combat onerous regulations and opposition from the taxi industry, violated the Governmental Ethics Ordinance by lobbying city officials and failing to register as a lobbyist.

Plouffe, who served as campaign manager and White House adviser to President Barack Obama, joined Uber in August 2014 and served as its senior vice president of policy and strategy.

The San Francisco-based company sent a letter to the ethics board objecting to the size of the fine, Chicago officials said in a statement on Thursday after the board's February 15 decision was made public.

Uber argued that Plouffe should be fined a maximum of $1,000 for the violation, the statement said. However, the ethics board said that Plouffe lobbied Chicago city officials on November 20, 2015 on behalf of the company without registering until April 13, 2016, culminating in the $90,000 fine.

The ethics board also fined the ride-hailing service $2,000 for the violation. Plouffe and Uber officials were not immediately available to comment outside US business hours.

Plouffe now works for Mark Zuckerberg's philanthropy organisation, the Chan Zuckerberg Initiative.